The human remains found in the search for missing student Antinette "Toni" Keller were so badly burned that an autopsy will not be possible and more testing will be needed to identify them, police said today.

The remains were found late Saturday in a DeKalb, Ill., park where investigators were searching for the missing 18-year-old Northern Illinois University art student.

"The investigation is proceeding as a homicide investigation," DeKalb Police Chief Bill Feithen said today at a news conference. "Due to the state of the burnt remains, an autopsy is not viable."

"Forensic experts have identified the remains as human," he said. "Whether these remains are Toni's or not could take some time."

The remains were found near items that appeared to be things that witnesses said Keller had with her, or was wearing, when she was last seen, Feithen said.

More than 40 police officers from the DeKalb County major case squad are working on the investigation with support from from six other law enforcement agencies, including the Illinois State Police and the FBI, he said.

"We have continued to interview persons, whom we believe may have information relative to this case," he said. "To date we have spoken to approximately 50 people, some more than once."

Keller, an 18-year-old freshman, went missing on Oct. 14 after setting off alone into Prairie Park at around noon. The young woman was last seen at her residence hall, when she told fellow students she was going to the popular park to get ideas for an art project.

"She just told the people she was going into the forest, which she did all the time, to do her artwork because that's a nice way to relax and have your art feel going, and she always came back before dark," Jamie Feather, one of Keller's friends, told ABC Chicago station WLS-TV. "She was supposed to meet someone the next day and never showed up."

According to Keller's cousin and family spokeswoman, Mary Tarling, Keller had made arrangements to see family and friends last weekend, and the family realized she was missing when she did not turn up at home Oct. 15.

NIU police immediately began a search once a fellow resident at Neptune North residence hall reported her missing on the evening of Oct. 15, Feithen said.

The Prairie Woods sit just south of the school's campus in DeKalb. Large portions of the park were closed to the public today as investigators searched the area.

According to Tarling, Keller's mother was hospitalized over the weekend due to stress after she was told that remains had been found and the case had been reclassified as a death investigation.

A posting from her family on the Facebook page set up to help find her, "Missing Antinette Keller" read: "Thank you for the outpouring of support. It is all this help from everyone here at NIU and the community that will bring Toni home. Please keep it going! Toni, we love you!"

Keller, originally from Plainfield, Ill., is a freshman at NIU and though she has only been on campus for a couple of months, word of her disappearance has her friends worried.

"This is the first time this has happened. It is frightening, and hopefully she is OK wherever she is at. We're hoping that nothing has happened to her," her friend Sydney LaPorte said.

Keller is described as 5-foot-6 and 130 pounds, with brown hair and blue eyes.

Anyone with any information on the whereabouts of Keller is asked to call a hotline set up by police, (815) 753-4648.